Device for the reproduction of wave motion



Sept. 18, 1928.

H. G. DORSEY DEVICE FOR THE REPRODUCTION OF WAVE Filed Sept. 21, 1923 2 Sheets-Sheet n sin a. s 63 3 IN VEN TOR.

sept 18, 192s.

I H. G. DORSEY DEVICE FOR THE REPRODUCTION OF WAVE MOTION Filed Sept. 2l, 1923 Y 2 Sheets-Sheet 2 Patented Sept. 18, 1928.

Uliiiif STATES HERBERT GROVE noRsEY, or' GLOUCESTER, MASSACHUSETTS;

DEVICE son THE REPRODUGTION or WAVE Horton.

Application filed September 21, 1923. Seli/a1 No. 626452,87.y

My invention relates to the reproduction of Wave motion for sound, electricity or for any wave Whose energy can he 'inside to actuate a diaphragm or sonic similar means. in which the vibration o1 the diaphragm or siinilur means operates to change the relative angle of incidence of a beanrof light upon a mirror, rotatable by the diaphragm and thereby reproduce the Wave motion of the energy sourfe by reflection from the mirror uponV a. revolving mirror und then upon a Screen.

An object of this invent-ion is to provide an instrument capable of reproducing any wave motion but more particular is associated with the reproduction of sound and electrical vibrations such that the -ziinplitudes and changes in the amplitudes of the Wave may be made visible to the observer.

For the nithul reproduction of any Wave motion so that the :nnplitudes of the produced visible Wave shall he proportioned to the amplitudes of the source Wave, it is neccssary to have a system that will not amplify one wave frequency inore than another. It is well known in the :irt that diuphrugms commonly used in the telephones und the like instrinnents have definite resonant frei'uencies, und that Waves of these frequencies are great-lj.7 eiiipliod :is compared with other non-resonant frequencies in their reproduction hy means of resonant duphriignzis. In my invention I employ a diaphragm whose resoniint YfrequencjY is shove that of the frequencies or' the waves which are to he reproduced which diiiplirzigiii unido with e. high resonant point by causing internal stresses in the diaphragm hf; methods of cooling.

Another oliject of i y invention is to provide an easily adjustable insel iiiiisni for reflecting toe source of light upon the mirror actuated by the diaphragm and means for adjusting); the iiiii'ror.

Still. unrtlier object of my invention is to provide nio iis for keeping the mirror in permanent :idif liiient. A inrtl i' purpose of iny invention .is to facilitate the veasy projection oi Wave forms upon u screen or other ineens by means of the inirror actuated by the diaphragm throwing e benin upon a rotatniiiior.

Other purposes of iny invention will be noted from the description, construction and assembly of my `device as *will appear heieafter in the Specification and drawings of which;

Fig. l is a'sectional viewof my improved form of wave reproducing apparatus.

Fig. 2 is :i side view of the upper portion of the device. f

Fig. 3 is an enlarged detail drawngto the spindle sind thread.

t Fig. 4 is :mend view .of the parts shown in Fig. 3.

Fig. 5 shows another'means of mounting 'the thread upon the indie.

F 6 is e. sectiomsil) View Aof the mix-Dor and the actuating medlanis'm.

Fig. 7 is a modilfrm of the parts shown in Fig. 2. f y

Fig. 8 shows a side viewoftlie parts shown in Fig. 7.

Fig. 9 is n diagrammatic view of how light passes from the source to the screen.

Fig. 10 shows the complete'system for prof jecting the vibrations on a screen with a. ineans for rotating the mirror.

Fig. ll shows a modification of Fig. 10.

The present invention aims -to overcome some of the difficulties inherent in the prc vious instruments as disclosed in my Patent No. 1,017,399., and in the/:Bowlen English Patent 26,412 of Nov. 29th, 1907. Bowron for example7 specifically mentions that he had trouble- With the thread around the mirror spindle slipping, and I have found in my own experience that this slipping of the thread on the spindle may canse serious bother unless it is properly corrected.

In most of the rotating mirrors, as now constructed there is insufficient Control of the speed so that the mirror continually tends to change its speed of rotation, causing much inconvenience to the operator.

In the preferred form of the invention there is a. base, 20, in which the rod, 21, may be clamped at any convenient height by the clamping screw, 22, and carried by a threaded joint at the upper end of the rod is an el# bow, 23, which has a projecting cap, 24, and which supports a mirror 25, placed at 45 de grecs to the Vertical. The upper end, 26, of the elbow is fitted into the collar,27, of the casing, 28, so that the latter nmy be rotated about the elbow, 23. There is a groove, 3l, in the upper part of the elbow into which the screw 32, projects, which serves to hold the casing and the elbow together, and when the screw 32 is. tightenechit clamps the two together in any desired position# The front of the casing is closed by a lid, 34,*held by screws 35, and which has an opening closed by a lens, 36 inclined at'ari'angleso that'the top part leans toward the interior asfshown in Fig. l. Inside the casing, there is a frame, 37 into which is threaded-anfadjustingscrew7 .39 passing freely through the slot 4l in the casi'ng. l:'Ihe :screw 39, hasa conical 'point 40. In the casing 28, there is a' groove42v termi- .i nating in a'hole 43 into which there is placed a spring wire, 44 having a right angle bend 45 entering hole 43, andwhich servesito hold the frame vin the 4casing so 'it may rotate a slight amount. l

The frame, 37 may have the truss 46, either asan integral lpart of the frame or it may be a separate part 47, secured by screws 48 as shown in-Fig.'7i To the rear of the frame 37, there is rigidly attached a diaphragm" l,

. having its centreembossed at 52,-to which is fr; are'the jewels 66,.- forminga rotatable mount ing lfor the spindle 67. vvThe thread 70, passes around the spindle 67, and has its ends at tache'd tothe hooks 57 and 58.

The spindle 67, has a flat place 7l, to which is cemented the mirror 72, and another flat place 7 3 at .45 degrees to the flat place 7l, and around it passes the thread 70. T he purpose of the flat place 71 is such that the thread 70 bypassing around the sharp edgeso'f the fiat place obtains a better grip on the spindle, preventingthe latter from slipping. rlhe flat portions 7l and '73 are so related that when the mirror 72, is vibrated through any of its ordinary angles the thread 70 is operating on a cylindrical portion of the spindle 67 so that it transmits to the spindle a uniform motion proportional to the displacement of the dia phragm. If this relation between the two flat portions is not approximately maintained when the mirror is vibrating through I large vamplitudes the thread would be operating on a Aflat portion instead of the cylindricalportion, andconsequently would introduce distortion into thecurves.

` Another method which I have employed is using a loop of thread or ribbon instead of a single thread around the spindle, as shown in Figs. 3'and 4, Where one end of the loop 74 passes through the other end of the loop and around the spindle, so that the four portions of the loop are so related to each other that the stress on the spindle is evenly balanced. By this method of communicating the motion from the diaphragm to the spindle, there is no tendency to cause the ends of ythespindle to rotate about the points of contact of thepthreadwiththe spindle, thus decreasing the friction ofthe spindle in the supporting jewels.A I talsorgives a tighter grip on the spindle, producing less tendency to slipping;:furthermore-ait permits more rapid assembly since the loops may be made of a definite size beforehand" and. lassembled fby simply attaching oiie end of theloop Ytofonehook, passing the other end around the spindle and attaching it to the other hoolr when the bow 55, hasl been bent a slight'amount.

In either method of attaching, the bow i's bent before the thread is .atta'ched,`so'that when` the bow is released,v 'it 4produces a stretched condition, of. the thread so thatvit grips'the'spindle tightlyfi Infthis c ass: of instruments itcis'fdesirable that it be able to respond to a great variety.

phragm must either have itsown naturalI 'if frequency higher-than any. vfrequency one wishes to show, or else such frequencies .must produce forced Vibrations fon the vibrating system. Furthermore to ,sho-W At'helhigher' harmonics the whole' vibrating sy'stem'm'ust be kept as light as possible or lelse these han monies will be suppressed- The highl natural frequency may be Obtained by using a stift" diaphragm, but in this case it requiresv considerable energy' to put the diaphragm in vibration. In order to maintain the high natural frequency with thin material, and yet lceep a simple form of construction, the followingv method of attachment of the diaphr in has been devised. If the diaphragm and the ring to which it is soldered, are of the same material they`will both have the same coeflicient of linear expansion, and being at the same temperature when soldered, will cool tofvether and so leave the diaphragm in a natural condition. If, however the dia'- phragm can be held at a higher temperature than the ring, the latter cooled at a more rapid rate than the diaphragm, when they are both cooled to room temperature, the diaphragm is left in a stretched condition', thus allowing it to have a higher frequency than it would otherwise have.

If the metals are dissimilar, such as an iron diaphragm, and a brass ring, and they are soldered in the ordinary manner, the iron diaphragm not only will not be stretchedbut will be slightly buckled, whereas having the diaphragm at a higher temperature than the ring and coolinT the ring quickly, even the iron diaphragm may be left in a stretched condition.

lill

League 5.-.Onelmiethod-of arcomplishing this, is to have ithedimplnragmil, onahotv plate and. thering .oraframe ylZ on another, plate, justatrthe mltingpoint, ofsolider, which serves as a plateiim; the tranne. The dia-- phnagm, having. been brought to. a. temperature milch higher than the. melting point of solder, and having been moistened with sol.- deringifluid, or otherWiseprepared so that the solder will stick to it, the trame 37 is transferred quickly from .the hat plate to the and aheavy weight is. placed on atop) .of fthe framefthns pressing the frame -oanduthe diaphragm 51,: firmlvtogether. Ancold, air-blastis Vthen directed :upon the frame; and atx the same; time the heat supplryirthezplatesupportng the diaphragm is remnveda By` this method the ring is cooled soimuoh more rapidly. than the diaphragm,

2&1 that there: is: no tendency to stretch. the diaphragm until the two-are firmly united, and theirfhaphrzrgm. thencooling, more slowly will he' leittiim astretched conditionmethod of. puttin-g the diaphragm imfa-sliitcliredeondition which I have used is to put eonriigaitions or' indentations,` or both, into` the...diapliragm site-r it has been at.- tachedto the:trame, as shown in. Figs. 7 and 8f. .'Todo this a press. may be employed hav- :ingjtliefeorresponding sinffaces necessary to make-g-corrugations in. the diaphragm, and also slots running'through the dies so' that theftrussAGof thel frame may {itin-to the recesses,.whichi would have the effect ofrproducing-.eorrugations ivi-th radi-el indentations such, described, in. my :Patent 1,017,392 The frame be: madeup; of; the ring' 37, and a ,separate truss; part 47 secured to the ring bythe screwslS, in which case the diaphargm 5:1, havingbeen attached to the ring,

3??,-maybe corrugated in the regular inanner, well known toA thosev versed in the arl', and the, separate trusspart 4J then Yfastened into Dlaee.;

f vtilli another method I have employedto producen stretched diaphragm is to solder it'toatbrass. frame, in any convenient manner sueltas on a. heated plate and then hammer orsqueeze the ring perpendicular to the plane `otlthe diaphragm, so that the ring is stretchedl around the periphery thus stretchingthe diaphragm itself and raising its natural frequency from about 300 before hainmeringl to. about 1G00 cycles per second site?. After the hammering or squeezing' process, the `fra-me is turned in the lathe and given a finishing cut to fit the casing.

It Will be seen that these methods oi stretching the diaphragm to raise its frequency to a permanent higher value are different from the -Well known method oi' clamping the edge and screwing in a ringT to displace the diaphragm bodily, my method permitting a cheaper method to accomplish the v1sunevresult,inivhat is believed to be a novel manner; A noticeable feature-,ietf tliiesefmethQ ods of producingastlietched diaphragm is. that theV diaphragm. may he permanently. stretched after it is: put in. place which is: ad-l vantageous in many cases Where. it is desirable.A to obtain lightweight ldiaphragms .of high-pitch, l 'l w Another embodiment .ot this. invention is the unique way inwlziichthe light is transf. mitte-d from the. source-to the vibrating mire :Jer 72... by reflecting from the fixed; Inirror2'5..J This mirror may be silvered on the: snrl'aee, in which-case there is onlyione image of the source, or 'it amirror silvered on the second Vsurace. -Ordinarily, however,.i silvered ou .the second surfacethere'wlllbe formed twofimages o thesource, one llrrigfhher than the. otherpresulting in .a lack of sharp-J ness of the spot of' light so thaticurvesane not so welzldetined as they would be iii-there were only one imager Topmdarceare image only and still have. the advantage oa silver-ed' on the -second'surfacerisf'ihemirror is wedge shape,as shown in Fiightline incidenti light A. O. will beireflectedfm'tlzle direction. 0. in the well knowmmanmerofsniaking. the angle of incidence A.. @te D.' equal to. the angle of reflection D. O-'Ei..andz.the.ireflected light will follow the line..Oe.F.-. G; Eninsuch o.. manner thatA the image reflectedlzonm' the second surface'V will coincide with rei'iected .lirom the first .surface atiseine'dif constant, itis; only necessary te select the glass.

of such thickness and ot suchen'gIe and Wedge, as to! fuli-ll the necessary condition.

En practice this is easily done by looking.

at a spot. of light at a dista-nce from the glass equal to the distance O. E having: the; eye at.

a distance equal-to the-distance the-...source of ligl'it would beffrom1-the mirrorin actualuse, rotating` the glass until a single image ci the sofurce- Yot' light is seen. A11 ellipse is now cut from theglass, having themajor axes. in the plane of thefa-ngleof incidence. and rei'lection.. which insu-res that the lglass; when siivered will act as a-miirror,. fulfilling the condition above given.

niiet-'ner embodiment et this invention the method whereby .ther beam oi' light is reflected to the screenby a rotating mirror, vso that one may be able to see the shape of the curve projected by this improved form of apparatus. lt is of greatest importancel that a simple method ot control is employed to iiisiire uniform andV constant angular rotation of the mirror, and toohtain this result-l'. have fou-nd .it advantageous@ use theapparatus:

. used supporting the sprocket wheel of a bipower to rotate the mirror. w

as shown in Figures 10 and 11. Essentially the apparatus embodies a centrifugal governor but one adaptable to respond quickly to changes in speedfof the motor furnishing the Thelsourceof power to rotate the mirror 120 is furnished by a motor 101 mounted on a'base .100 as shown in Figure 10. To the shaft 102 of the motor is keyed orfitted a fan 103 rotated by the shaftu102. The fan 103 maybe of the type used'in vacuum cleaners, which forces the air out radially in the plane of rotation of the blades 104 so that as the blades 105, whichrrotate the shaft carrying themirrorxl'z, are forced upwards and outwards, they .catch less of the stream of the air whiclisi-mpartsthe necessary energy for rotation. l: The. b-lades 105 are made of" some springy material and of suitable thickness for the purpose consisting of' a fiat spring portion 106swhose one endis bent at right angles with thefiat portion to .form a leaf =.The otherend of the'spring is apart of a collar-108 fixed firmly on the shaft 109 carryf ing the mirror 1'20.- The Iblades, 105 with their bent leaves and collar portion, i'nay be stamped as one piece of metal, and the collar fitted and joined about the shaft 109.

:f The shaft 109'is supported for rotation by two bearings 110 and111, similar to the kind in the shaft 109 serves to hold the upper en d of the shaft 118 in a central and upright position while the lower` end of the shaft 118 fits into the hole of the lower cap 122 screwed in the shaft 109 and rests upon a spring 121.

-The shaft 118 has also a collar 123 which Screws into the enlarged but rectangular portion of rod 124 which is free to move in slots 125 diametrically opposite in the hollow shaft 109. Below the-rod 124.4 is a collar 126 free from the shaft 109, but having supporting rods 127 connecting to the flat spring portion 126 in such a manner that when the small rod 124 moves downward, bearing upon the collar l 126, the rods 127 are made to bear upon the spring pieces 106, thus forcing the leaf portions 105 downward into the stream of air.

The rod 124 is made to bear upon the collar 126 as above described by means of the screw 128 threaded through the bracket 129 into the .shaft 118. The screw 128 has a cone bearingon its end, ,fitting into va vsmalljewel bearing 140, in the top ofthe shaft 1-18 so that the friction due to the rotationof the shaft will at once be uniform and slight. By screwing the screw 128 downwards against the upward thrust of the spring i121 the rod v1211V bears upon the collar V126 which' forces the spring piece'106 and the leaves 105 downward into the stream of;air createdlby the motor fan 103.

T he beam oflight as evident from Fig.^10 comes into the mirror 25, and isreflected -to the mirror 67, through .thelens 36to themir.- ror 120 which rotates and isadaptedito throw iight upon a screen. The purpose Vof'. the ap` paratus shown in Fig. .10 is to maintain acon-f stant speed of the rotating mirror 120lso` that the light thrown upon the .screen is spreadf unit'ormiy at all times. .This is essential in giving a true picture ofthe wave motion op erating thesmall mirror 672 'w in Fig. 11 is shown a. modified formof the construction of Fig-'10. Here`r the motor: is mounted horizontally 'asY shown in.130,'while the mirror 131is mounted vertically. The set screw 132 serves the same purpose as that of. 128 and so all the restof the-apparatus'f Mo; tion is impartedV to the verticalhmirrorthrough the beveled gears133 and 134,? the latter of whichis driven by the blades 135 which receive their energy through the fan' 136 rotated by the motor shaft 13 f lf' one wishes to increase' the speed of roiT tation it is only necessary to' turni the set screw 128 or 132 in Figs. 10 and A11 according to which modification is employed indirectly forcing the blades 105 downward intoV the4 maximum energy of the: air Stream. Not only will the speedbe increased-through `method just mentioned 'out there will also b e atendency to increase the speed through the governor action of the spring pieces. When the' speed of the blades 105 are decreased the centrifugal action, as is well known decreases the speed and thus there is a double action in the regulation, furnishing sensitive'control.

This form ol rotating mirror and governor enables one to control the speed of the motor `while it is running, so that successive waves will be superposedon each other just as with a synchronous motor, sinceafter the, correct speed is reached the governing action of the spring blades will maintain it. Y

Having now described my invention, AI l claim:

1. An apparatus for producing wave motion comprising two unit instrumenlts,' the first of said units, comprising a diaphragm, a vibratable mirror, mounted upon an axis, parallel to the plane of the diaphragm, transmission means for transmitting the vibration of' the diaphragm to the mirror, a second mirror within the casing of the said first unit adapted to reiect a beam of light .upon the first mirror and a third uniformlyrotatlng mirror, in the second of said units adapted to receive and reflect the light of said first mirror.

2. In an apparatus for producing wave motion, a diaphragm, a. rotatable mirror mounted upon an axis parallel to t-he plane of the diaphragm, transmission means 'for transmit-- ting the vibration of the diaphragm to the mirror, a second mirror, positioned at an angle approximately 45 degrees from the horizontal, and adapted to reflect a beam of light to the said first mirror.

3. In an apparatus for producing wave motion, a diaphragm, a rotatable mirror, mounted upon an axis parallel to the plane of the diaphragm, transmission means for transmitting the vibration of the diaphragm to the mirror, comprisingl a bow mounted upon the diaphragm, a cord, a spindle mounted perpendicular, and in the same plane with the cord of said bow, said spindle containing a fiat portion whose edge grips the cord wound about the spindle, said mirror mounted upon a second flat portion of the spindle, whereby the mot-ion of the diaphragm is transmit-ted to the mirror without any slipping upon the spindle.

4. In an apparatus for reproducing wave motion, a diaphragnna reflecting means vibratable about an axis parallel to the plane of the diaphragm, positive means for transmitting vibrations of the diaphragm to said reflection means, and a second reflecting means so positionedas to reflect a beam of light to the said first reflecting means.

5. In an apparatus for showing wave motion, the combination cf a diaphragm, a vibratable reflecting means associated therewith, a second reflecting means positioned to th'row a beam of light on said first refiecting means and thence to a third rotating reflecting means having adjustable governed speed.

6. A pivoted spindle having indicating means, a tensioned driving means encircling a portion of said spindle, and a fiattened place on said portion to prevent slippage of said driving means.

HERBERT GROVE DORSEY. 

